Study of CFS-strengthened RC beams with shear key

It is sometimes known that when the bonding strength of reinforced concrete (RC) flexural members strengthened with fibre sheet composites is sufficient, debonding failure does not occur until the sheet fails. However, many researches have reported that debonding failure occurs frequently before the fracturing of the sheet itself at early loading stages, even though the bonding length is sufficient. On the grounds of practicality, it is very important to prevent debonding at the ends of the soffit plate using mechanical anchors and to eliminate the possibility of debonding failure. This study was carried out to evaluate the effectiveness of shear keys and U strips on the flexural behavior of RC beams. The ply numbers of carbon fibre composite sheet (CFS), location of the shear key, and existence or non-existence of the U strip were selected as the main test variables. The test results showed that the behaviour of a beam having shear keys near the supports, non-existent U strip, and one-ply CFS along the overall length and the other ply along the centre half-length showed the most apparent improvement compared to the other beams.